The light-magnifying
qualities and improved resolution of photomultiplier-aided, SEM-based
cathodoluminescence systems (scanned-CL) provide detailed images of grain
textures that are useful in provenance analysis of sandstones. Scanned
CL imaging can be further enhanced by using color filters to produce synthetic
color images or limited wavelength images. These images commonly reveal
textures that are invisible or obscure in panchromatic gray-scale CL images.
Color scanned CL of quartz grains is particularly useful in identifying
internal or external authigenic quartz cement that predates deposition.

Examination
of over 100 siliciclastic units has shown that CL textures in quartz grains
are not only useful for identifying the lithological provenance of some
grains, but also the predepositional deformational history of some grains.
This deformational history can provide the structural provenance of the
grain. For example, grains that have undergone significant brittle deformation
prior to deposition are typically distinguishable using scanned CL. If
scanned CL images are not acquired, broken and recemented quartz grains
can be mistaken for ductily deformed grains with discontinuous undulatory
extinction.

Scanned
CL imaging of feldspar and zircon grains and siliceous rock fragments
can also aid in sandstone provenance analysis. Zircon grains typically
show intense and complicated zoning in scanned CL images. Potential exists
for differentiating between plutonic, volcanic, and metamorphic zircons
based on this CL zoning, although there is some ambiguity and further
study is needed. Both individual zircon grains and zircons contained within
other types of grains provide opportunities for interpretation. Siliceous
rock fragments commonly show complex CL textures. In CL images, some chert
grains show distinct evidence of biologic components, while others show
layered structures that suggest chemical precipitation. Scanned CL imaging
has the potential to enable significant advances in the discrimination
between microcrystalline quartz of sedimentary origin and that related
to alteration of volcanic rocks. Feldspar grains do not show the range
of CL textures seen in quartz grains, but textures reflecting the origin
or predepositional alteration of the grains can be observed.